Rammed by a Norwegian freighter, the nuclear sub Neptune (the "gray lady" in question, captained by Charlton Heston) sinks 1400 feet before coming to a terrifyingly uncertain rest on a deep sea canyon outcrop. The Neptune's position prevents rescue via standard submersible, leaving an untested sub prototype, the Snark, commanded by navy rebel David Carradine, as the only chance to avoid death for the Neptune's crew. Christopher Reeve's first movie, in a bit part.